Bewick's Wren Range Expansion?

I got me another bird to add to my Idaho state life list. Bewick's Wren. I had seen them on a dozen occasions in Arizona, but not in any other state. The more I learn about this cool little wren, the more interesting it becomes, especially as it relates to recent range and distribution changes.

I found these two singing Bewick's Wrens at my beloved Avimor in the Boise foothills; a place I have birded regularly for a few years now. A couple years ago, I thought I had a glimpse of a Bewick's Wren in a mixed flock of warblers and other birds at Avimor, but it was too brief an encounter for me to feel confident of the i.d. at the time. This recent sighting gives me a little more confidence about what I saw previously. Plus, a handful of other birders have been seeing and hearing Bewick's Wrens in the same general area along Spring Valley Creek for the last couple of years while I was away living in Utah.

While the Bewick's Wrens are declining/disappearing in the eastern United States, perhaps due to competition with similar species, in some parts of the interior west Bewick's Wrens seem to be expanding. Idaho bird records legend, Shirley Sturts, informs me that the first Idaho records occurred in October 1982 and that they have been seen in Idaho every year since. It appears that the wrens expanded their range eastward along the Columbia River into Idaho. In the 1980's and 90's they continued to expand north and southward from the Lewiston area, perhaps following the Snake and Salmon rivers upstream. Cliff Weisse also suggests that they may be expanding their range northward from the Great Basin. The first reported Bewick's Wren in Idaho's Treasure Valley (greater Boise area) wasn't until 1998. In 2001, one was identified during the Boise Christmas Bird Count. Still on the list of review species for all of southern Idaho, reports to the IBRC from southwestern Idaho seem to have become more regular since 2010, which coincides with when they started to be seen at Avimor.

While their range expansion is not as dramatic as the Eurasian Collared-dove, it is still fast enough to be easily observed over my life time. Range maps in most field guides and even the latest apps have not yet accounted for their increasing abundance in Idaho.

Our understanding of potential conflicts and competition with other species will surely play out over time. They are found in similar habitat and appear to feed like House Wrens, Ruby-crowned Kinglets, and Black-capped Chickadees. They seem to be aggressive defenders of territory, so they may expel species that have historically inhabited the area.

This last butt-shot image I include because it shows the rich velvet chocolate head and back, the typical barred wings and tail feathers of wrens, and the gray underparts. The first couple of images show the prominent white eye-brow (supercilium) and the white fluffy throat. I also notice the two-toned bill, dark on top, lighter on bottom.

I thought I was hearing a Song Sparrow singing, but was surprised when I put my Swarovski binocular on it. Their songs are surprisingly similar...at least my neck of the woods. It was also interesting to find singing conspicuously at this early date in February. I heard and saw it perform several different types of vocalizations. It sometimes approached me as I was intruding upon its territory.

It will be fascinating to continue to monitor numbers and range expansion of this cool little wren. eBird makes this kind of citizen science and analysis very accessible to regular joes like me.

I've now seen all the Idaho wrens at Avimor now except Marsh. Marsh Wren is still a real possibility given the wetlands and marshy areas at Avimor. Maybe I just haven't looked hard enough yet.